JPS58159560A - Controller for toner supplementation - Google Patents

Abstract

PURPOSE:To prevent the toner density of a developer from increasing abnormally by providing a detecting means for the condition before development which exerts influence upon measurement information, and varying the level of the measurement information for interrupting toner supplementation according to detection information. CONSTITUTION:The image exposure of an original including a reference density piece fitted to the reverse surface of the front end of a platen is carried and then toner development is performed; and the toner density is measured by a density measuring means 10 and toner supplement is controlled according to the measurement information is higher than a specific level or not. The potential of the reference density piece before the development is detected by a potential sensor 13 and a potential sensor driving control circuit 14 allows a voltage output circuit 15 to output a reference voltage VO to a comparator 16 when the detected potential is higher than a specific value, but to output another reference voltage Vh when it drops below the specific potential; and the output voltage is compared with the output V of a photosensor 10a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a copying machine or the like that develops an electrostatic image using a developer consisting of toner and carrier. The present invention relates to an improvement of a toner replenishment control device for a replenishment tank.

The conventional toner replenishment control device as described above includes a developer density measuring means and a toner replenishment control means for controlling toner replenishment based on the measurement information, as shown in Japanese Patent Publication No. Sho U3-/6199, for example. It is known that it has the following. Since such a device primarily controls toner replenishment so that the developed density remains constant, it is an excellent control device in that it can more directly guarantee the recorded image density. It is. On the other hand, a developer toner device that measures the magnetic permeability and color density of the developer is preferable from the point of view of keeping the toner concentration of the developer constant; This is only an indirect guarantee that the recorded image density will be constant. Therefore, in order to finally obtain a clear recorded image, it is preferable to use a toner replenishment control device that controls t w A by the developer density, but this also has the following problems. In other words, even if the developed density is determined by the developed density of the reference density piece, the developed density does not depend only on the toner density of the developer, but rather the developed density does not depend only on the toner density of the developer, but rather on the basis of the density of the image recorded on several hundred sheets in succession. If images are recorded continuously under extreme atmospheric conditions such as 5°C and 1.20% RH or less, the electrostatic image potential may change sharply, causing the developer to Even though the toner density is appropriate, the developed density may decrease. Then, the toner replenishment control means continues to replenish toner in order to guarantee the developer concentration, which causes the toner concentration of the developer to become abnormally high, and toner often scatters from the developing device. The scattered toner may adhere to the lens or mirror of the exposure device, the charger or transfer device, or reduce the clarity of the recorded image.

Therefore, the present invention has been made to solve the above-mentioned problems of a toner replenishment control device that controls toner replenishment based on developer density. The present invention provides a toner replenishment control device that prevents the toner concentration of a developer from becoming abnormally high based on detected information.

That is, the present invention provides a means for measuring the density of an electrostatic image developed with a developer consisting of toner and a carrier, and a toner replenishment control means for controlling the replenishment of toner to the developer based on the measurement information of the means. In the toner replenishment control device, the toner replenishment control device is configured to include a detection means for pre-development conditions that affect the measurement information, and to change the level of the measurement information for intermittent toner replenishment based on the information of the detection means. This feature prevents the toner concentration of the developer from becoming abnormally high.

Hereinafter, the present invention will be explained based on illustrated examples.

FIG. 1 is a configuration diagram of main parts of an electrophotographic copying machine according to the present invention;
Figure 2 is a bottom view of the document table, Figure 3 is a graph showing the relationship between developer toner concentration and toner adhesion amount during development, and Figure q is a graph showing the relationship between developer toner concentration and developer toner concentration using a reflected light receiving photosensor. FIG. 5 is a graph showing the relationship with the photosensor output when this is done, and FIG. 5 is a schematic configuration diagram showing an example of the toner replenishment control device of the present invention.

The copying machine shown in Fig. 1 has a reference density piece λ for measuring the developed density attached to the lower surface of the tip of the document table as shown in FIG. When the photoreceptor drum j rotates in the direction of the arrow, the charger II uniformly charges the surface of the photoreceptor drum S, and the lamp 3a of the exposure device 3 lights up. The exposure device 3, which includes a document table/or a lamp 3a, a reflector 3b, a mirror 3c, a lens 3d, etc., moves horizontally in synchronization with the rotation of the photoreceptor drum, thereby exposing the photoreceptor drum j.
The image of the document M including the reference density piece λ is exposed to the uniformly charged surface, and the electrostatic image formed on the photosensitive drum S is developed with toner by the developing device B. The toner development for the document M is transferred to the recording paper P by the transfer device 7, and the transferred recording paper P is transferred to the separator g.
Copying is performed by separating the light from the surface of the light drum j and ejecting it to the outside of the machine via a fixing device. Then, the toner development of the standard density piece λ in the toner development passes through the transfer device 7 and the separator r position without being transferred to the recording paper P, and the toner development density is measured by the density measurement means 10, Depending on whether the measured information is above a certain level, toner is replenished from the toner replenishing device // to the developing device B, or the toner is corrected. This prevents a decrease in the developer concentration due to a decrease in the toner concentration of the developer, and even if there is fatigue of the photoreceptor drum j, a change in atmospheric conditions, or a change in exposure conditions, the toner concentration of the developer will not change. Therefore, the development density is kept constant. In addition, when developing an electrostatic image with reference density strip λ, in order to prevent fog from occurring during development, the bias voltage applied to the developing device B should be adjusted to match the charge of the electrostatic image. The voltage is controlled to be equal to but lower than the bias voltage applied when developing the electrostatic image of document M with the same polarity, and when developing the electrostatic image (B) of document M, the bias voltage is applied to the electrostatic image. It is preferable to control the voltage to a voltage that has the same polarity as the charge of the image and is sufficiently higher than the potential of the background portion. As a result, the developed electrostatic image of the reference density piece λ has a uniform density with extremely little edge effect, and the developed electrostatic image of the original manuscript M becomes clear with respect to the background portion.

The surface of the photoreceptor drum j that has passed the density measuring means/θ position has toner removed by the cleaning device/2 to become a clean surface, and as the photoreceptor drum j continues to rotate, the surface is eroded, charged, and exposed. is repeated to make the next copy.

The above description is the same as that described in the conventionally known Japanese Patent Publication Sho≠3-/1/ri No. 9.

In other words, since the constant development density is guaranteed by changes in the toner concentration of the developer, in this case, if the decrease in the development density is due to a cause other than the toner concentration of the developer, the toner concentration of the developer may become abnormal. I'm used to paying high prices. This relationship will be explained with reference to FIGS. 3 and 7.

In FIG. 3, under normal conditions, the relationship between the developer toner concentration and the amount of toner adhesion during development follows a curve 0. Correspondingly, the photosensor output for measuring the developed density also changes as shown by curve 0 in FIG. Then, the photo sensor output ■ is V>V with respect to a constant level Vo.

When this happens, the toner replenishing device/l shown in Fig. 1 replenishes toner, and VS Vo stops toner replenishment, so the toner concentration of the developer is kept constant at approximately To, and the concentration becomes too low to cause problems such as internal contamination. The limit Tt will not be exceeded. but,
When making several hundred copies in a row, at r℃,
When continuous copying is performed in an abnormal atmosphere such as 20% RH, there is a relationship between the developer toner concentration and the toner adhesion amount of the developer. In that case, the same constant level V
If toner replenishment control is performed using the photosensor output V based on o, the developer toner concentration will be kept constant at approximately Te, which will exceed the concentration limit Tt and cause problems such as dirt inside the machine.

Therefore, when the points described below become the main points of the present invention, and as shown by the curve E in Fig. q, the photosensor output V
The constant reference level ■o for controlling toner replenishment is changed to a constant level Vh below the photosensor output Vt corresponding to the developing (D)-J-1 adhesion amount Mt, which is the limit for obtaining satisfactory copies, and then If toner replenishment is controlled using the photosensor output V based on a constant level Vh, the toner concentration of the developer will be maintained at Th below the concentration limit Tt, and the amount of toner adhesion during development will be kept at the limit. The toner adhesion amount is Mt or more, and the result is that clear copies are guaranteed without causing problems such as internal dirt. In the example shown in Fig. 5, it is determined whether the relationship between the developer toner concentration, the toner adhesion amount during development, and the photosensor output is as shown by the curve E in Figs. 3 and 1, based on the electrostatic image potential before development. Based on the determination result, a certain level t[(q) of the toner replenishment control is adjusted.

In FIG. 5, the potential sensor 13 is driven by the potential sensor drive control circuit /F to detect the potential of the electrostatic image of the reference density piece in FIGS. 1 and 2. When the detected potential is above a certain potential, the reference voltage output circuit tS outputs the reference voltage o to one terminal of the comparator/g, but when it becomes lower than the certain potential, it outputs the reference voltage Vh. . The state where this detected potential is above a certain potential gives the relationship of curve 0 in Fig. 3 and Fig. ψ.
A state where the detection potential is lower than that gives the relationship of curve E.

Accordingly, the comparator 1 compares the output of the concentration measuring means/θ of the photosensor/θa with the reference voltage vo in the state of the relationship shown by the curve O, and outputs the amplifier circuit only between ■>700.
A toner replenishment signal is output to the toner replenishment control circuit H via the toner replenishment control circuit H to replenish toner from the toner replenishment device // to the developing device B.
h, toner replenishment from the toner replenishing device /l to the developing device B is performed only between V and Vh. As a result, it is possible to obtain the excellent effect that the toner concentration of the developer does not become excessively high as described above (lθ) 5, and that clear copies can be made.

In addition, in FIG. S, the same functional members as in FIG. 1 are indicated by the same symbols, and lθb is still a photodiode.

The present invention is not limited to the examples described above, and for example, the surface of the photoreceptor drum j that has been charged by the charger V may be used as the detection surface by the potential sensor 2, or the reference density strip λ
It is also possible to use the development of the charged surface, which is not exposed to light, for measuring the developed density, without providing a. In addition, in cases where fluctuations in the electrostatic image potential on the photoreceptor drum j are mainly affected by exposure conditions, the reference voltage for toner replenishment control can be changed by detecting changes in the reflected light intensity of the reference density strip. You may also do so.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts of an electrophotographic copying machine according to the present invention;
Figure 2 is a bottom view of the document table, 3rd page 21ff is a graph showing the relationship between developer toner concentration and toner adhesion amount during development, and Figure 1 is a graph showing the relationship between developer toner concentration and development toner concentration, and Figure 1 shows that the developer toner concentration and development concentration are measured using a photo sensor that receives reflected light. FIG. S is a graph showing the relationship with the photosensor output in the case where the toner replenishment control device of the present invention is used. l...Original table, λ...Reference density piece, 3.
...Exposure device, G...Charging device, 5...Photosensitive drum, 6...Developing device, 7-...Transfer device,
t...Separator, 9...Fixing device,
IO・-・Concentration measuring means, /θa・・Photo sensor,
lθb...Photodiode, //...Toner supply device, /2...Cleaning device, 13...Potential sensor, /ll...Potential sensor drive control circuit, t3...Reference voltage output circuit , /4... comparator, /7... amplifier circuit, 7g... toner replenishment control circuit. Patent applicant: Konishiroku Photo Industry Co., Ltd. Figure 1 - Figure 2

Claims (1)

[Scope of Claims] 1. Means for measuring the density of an electrostatic image developed with a developer consisting of toner and carrier, and toner replenishment control for controlling toner replenishment to the developer based on the measurement information of the means. The toner replenishment control device has a means for detecting conditions before development that affects the measurement information, and is configured to change the level of the measurement information for intermittent toner supply based on the information of the detection means. A toner replenishment control device characterized by: 2. The toner replenishment control device according to claim 1, wherein the detection means is an electrostatic image potential detection means.